Performance of KRAS mutation detection in plasma exosomes from patients with early-stage colorectal cancer.

BACKGROUND

Liquid biopsy is a minimally invasive method, which is an alternative to tissue biopsy in solid cancers to detect driver mutations, monitor treatment responses, and estimate prognosis. Exosomes are a group of extracellular vesicles that are detected in body fluids and are more stable than cell-free DNA and circulating tumor cells. Genetic data of parental cells can be packaged into exosomes, analysis of which could help determine the genetic modifications of cells before the emergence of disease symptoms. Here, we sought to investigate the KRAS mutation detection in exosomal DNA extracted from the plasma of patients with colorectal cancer.

METHODS

This study was conducted on 42 colorectal cancer patients with stage I-III. First, exosomes were purified from the plasma of patients using Size Exclusion Chromatography (SEC), and then DNA was extracted from the samples using the phenol-chloroform-isoamyl alcohol (PCI) method. Next, the presence of three KRAS variants was examined using the Intplex quantitative PCR method.

RESULTS

The mutant allele frequency was measured with a sensitivity of 0.01%. About 85% of the tested exosomal DNA samples had one or two KRAS mutations. The measured mutant allele frequency had a median of 1.18% (with a range of 0.01-63.33%). Moreover, we evaluated the concordance of mutation detection between patient exosome and tumor tissue DNA samples.

CONCLUSIONS

We concluded that the investigation of mutation in genetic contents of exosomes extracted from the plasma of cancer patients at early stages could be performed with high sensitivity and could accelerate determination of the best therapy process for patients.